I have a KEF 25b Subwoofer that suddenly started Buzzing (with or without cables attached). It also smells like something is burning. Kef offered to fix it for $110 which is their flat rate (assuming it can be fixed), plus shipping both ways - ugh! My question is does this sound like something major or minor? Is it something I can fix myself? Is it worth fixing or should I start looking for a replacement? Thanks for any help you can offer!